You are either blind, stupid or just want a man just to have one. If this boy does not introduce you to his friends, he is:

ashamed of you

has a wife

has a girlfriend

has another woman

dating others

sleeping with all

But most importantly, he is lying. Nothing is so strange or weird about behavior that is obvious. Seems to be obvious but not to you, I can see that. Just because a man uses the word fiance or engaged does not mean that he is not using it with another woman or even a wife.

Dump the bastard! He is a lying, scum bag and you need to get away from him. This will not end well and you will get hurt when you find out some day that he also children and a wife.